Most manufacturing processes use gases and produce exhaust streams that may contain recyclable components. Many of these components are expensive and therefore if recycled could significantly reduce production costs. In addition, the exhaust gases often contain components that are toxic, reactive or difficult to handle. This is especially true for the manufacture of semiconductor devices that employ expensive and dangerous gases in the production processes.
For example, many semiconductor manufacturing processes use or produce gases having very high global warming potentials, such as SF6, C2F6, and CF4 that if recycled would present no environmental concern and would reduce overall costs related to the abatement or disposal thereof. Other possible recyclable components in the exhaust streams include Xe (xenon), Kr (krypton), CF4 (carbon tetrafluoride), C2F6 (hexafluoro-ethane), SF6 (sulfur hexafluoride), NH3 (ammonia), and components that do not undergo significant reaction or decomposition with pure water, or various water containing solutions such as KOH (potassium hydroxide), NaOH (sodium hydroxide), or H2O2 (hydrogen peroxide). Again, if these components were recycled, a significant overall cost savings could be realized.
Currently the process gases from semiconductor etch or deposition processes are not recycled. Rather, the process gases are normally disposed of after use in the process chamber. As noted above, these gases may be expensive and may include dangerous properties. In addition, it is common for a relatively large excess of process gases to be used in the production step and therefore a high percentage of the process gases are not consumed during the production step. This results in a greater expense and risk. Recycling just the unused process gases could provide a significant cost reduction for the process.